Wireless local area network (WLAN) technology has evolved rapidly over the past decade. Development of WLAN standards such as the Institute for Electrical and Electronics Engineers (IEEE) 802.11a, 802.11b, 802.11g, and 802.11n Standards has improved single-user peak data throughput. For example, the IEEE 802.11b Standard specifies a single-user peak throughput of 11 megabits per second (Mbps), the IEEE 802.11a and 802.11g Standards specify a single-user peak throughput of 54 Mbps, and the IEEE 802.11n Standard specifies a single-user peak throughput of 600 Mbps. A new standard, IEEE 802.11ac, promises to provide even greater throughput.
Some wireless communication systems utilize multiple transmit antennas and multiple receive antennas to increase the number of signals which may be propagated in the communication system and/or to compensate for deleterious effects associated with the various propagation paths, and to thereby improve transmission performance. Such a system is commonly referred to as a multiple-input, multiple-output (MIMO) wireless transmission system and is specifically provided for within the IEEE 802.11n Standard. Further, the 802.16 standard, or WiMAX, applies to cell-based systems and supports MIMO techniques. Generally speaking, the use of MIMO technology produces significant increases in spectral efficiency and link reliability of wireless communication systems, and these benefits generally increase as the number of transmit and receive antennas within the MIMO system increases.
A MIMO channel formed by the various transmit and receive antennas between a particular transmitter and a particular receiver includes a number of independent spatial channels. As is known, a wireless MIMO communication system can provide improved performance (e.g., increased transmission capacity) by utilizing the additional dimensionalities created by these spatial channels for the transmission of additional data. However, instead of using all of the various different transmit and receive antennas to form separate spatial channels on which additional information is sent, better transmission and reception properties can be obtained in a MIMO system by using at least some of the various transmit antennas of the MIMO system to transmit the same signal while phasing (and amplifying) this signal as it is provided to the various transmit antennas to achieve beamforming or beamsteering. Generally speaking, beamforming or beamsteering creates a spatial gain pattern having one or more high gain lobes or beams (as compared to the gain obtained by an omni-directional antenna) in one or more particular directions, while reducing the gain over that obtained by an omni-directional antenna in other directions. If the gain pattern is configured to produce a high gain lobe in the direction of each of the receive antennas, the MIMO system can obtain better transmission reliability between a particular transmitter and a particular receiver, over that obtained by single transmitter-antenna/receiver-antenna systems.
In some MIMO communication systems, multiple bit streams may be encoded for transmission via the MIMO channel using multiple channel encoders, and a single receiver may receive and decode the multiple encoded bit streams. For example, a single transmitter, such as within a user device or a base station, may include multiple channel encoders, and a single receiver may receive and decode the transmissions from the single transmitter. As another example, a plurality of transmitters, such as distributed among a plurality of user devices, may each include a channel encoder, and a single receiver, such as a base station, may receive and decode the transmissions from the plurality of transmitters.